1. Field of the Invention
This invention concerns a device and a process for precipitating polymers from polymer-containing fluids (solutions, emulsions or suspensions) by means of at least one fluid. The purpose of the invention is to simplify the precipitation step, thereby making this device and process more commercially viable than the devices and processes currently available.
2. Description of the Prior Art
It is known to coagulate the latex in polymeric latex emulsions by means of acids and to thus recover the polymer. An acid-containing fluid is formed as a by-product, which must either be reprocessed or disposed of- sometimes at considerable cost.
Dissolved, suspended or emulsified plastics can be recovered by evaporation of the solvent. However, this process requires a considerable energy input, particularly in those cases where the solvents have a very low concentration of plastic.
A process for the continuous recovery of polymers from an emulsion is described in EP-0,030,994. The latex is fed by means of a steam-charged nozzle laterally through a plurality of channels, the latex being divided into a particle dispersion. This dispersion is passed through a steam-heated heat exchanger of the tube-in-tube type. The dispersion consists of the polymer in the form of solid particles together with liquid particles in a steam phase which contain the unconverted monomers and the steam. The steam phase is then separated off. In place of the heat exchanger, a washing stage can be used. The process is applied to non-tacky polymers; in the case of tacky polymers, blockages at the nozzles, heat exchanger and cyclone are to be expected. The lattices are aqueous emulsions of polymers; these do not contain any solvent which must be expelled by evaporation. The residence time of the dispersion of precipitated polymer in water is 0.1-1 second in the exchanger.
In German Patent Document No. 2,365,073, a device for precipitating plastics out of the solvent using heated water is described. A fluid containing the plastic and heated water are introduced under pressure into the device. The jets of this fluid, emerging through nozzles, pass directly into an atomization chamber, which contains evaporated solvent, evaporated water, and the precipitated plastic. The plastic drops downward together with water which has not evaporated and is separated from the gas phase. Because of the spontaneous transfer of the precipitated plastic and the heated water into the gas space, the liquid phase and the gas phase separate quickly from one another. Liquid residues and monomers contained in the precipitated plastic remain occluded in the plastic particles. The device, especially the nozzle for the fluid containing the plastic, can be cleaned only after the device has first been dismantled. A downward-tapering bracket fitted to the adjuster protrudes into the atomization chamber.